Electric discharge apparatus



May 14, 1935. w. UYTERHOEVEN ELECTRIC DISCHARGE APPARATUS Filed July 3, 1933 Pkg. 2.

Inventor: Wil Iehw Ugcerhoeven,

His At orneg.

Patented May 14, 1935 UNITED ,STATES PATENT OFFICE Willem Uyterhoeven, Eindhoven, Netherlands, assignor to General Electric Company, a corporation of New York Application July 3, 1933, Serial No. 678,952 In the hlctherlands June 30, 1932 7 Claims.

The present invention relates to electric discharge apparatus and particularly to glow lamps which employ hot cathodes coated with electronically active material. Tubes of this character usually contain one or more gases, or vapors, or a mixture of a gas and a vapor. During operation, a discharge is produced within the tube which is accompanied by light of an intense character.

It has been noted that after a long period of operation, and occasionally, shortly after the tube starts, a coating is ordinarily formed on the inside surface of the envelope and consists of a thin dark colored material which seriously obstructs radiation of the light. This phenomenon is believed to be due, in a large degree, to the evaporation of active material from the hot cathode.

An object of the present invention is to eliminate the presence of this layer so that a glow lamp of this character may operate at optimum efliciency. This object is carried out, in brief, by giving the anode a particular shape of surface, for example, an undulated configuration, consisting of projections and grooves. When a glow lamp is provided with an anode of this sort, it has been found that the material evaporated from the glow'cathode is deposited mainly in the grooves of the undulations and not on the walls of the tube. Thus, the envelope of the glow lamp is kept free of the opaque material. A satisfactory explanation of the manner in which this type of anode serves to prevent the active material from collecting on the interior of the envelope has not as yet been found but the phenomenon has been confirmed by numerous tests.

In addition to collecting the active material, the improved form of anode offers the further advantage that the dimensions of the anode can be decreased while the anode surface available for the discharge current remains the same. As a result, the anode intercepts a smaller portion of the produced light rays and thus serves to increase the light output and power economy of the tube. The improved shape of anode also offers additional mechanical strength to the member.

An exemplary embodiment of the invention is shown on the drawing, Fig. 1 of which illustrates a glow lamp provided with the improved form of anode, Fig. 2 is a plan view of the anode.

As shown, numeral I designates a bulbous form of envelope which terminates in a reentrant stem and press 2. Within the tube, preferably centrally located, there is a filamentary cathode 3 which may take the form of a tungsten helix coated with electronically active material, such as alkaline earth oxide. The filament is mounted in position, preferably transversely of the envelope, by means of a pair of rigid leading-in conductors 4 which are sealed in the stem. A tube 5 5 of insulating material may surround the portion of each of these conductors which projects beyond the upper surface of the press. On opposite sides of the cathode, preferably symmetrically mounted with respect thereto, there are a pair of anodes 6 which take the form of a ribbon, such as molybdenum strip, bent into.corrugated or undulated circular form as shown in Fig. 2 and positioned transversely of the envelope. The corrugations extend preferably in a direction toward the cathode, i. e. along the depth of the strip. As

in the case of the cathode, the anodes are mounted within the envelope by stiff conductors I secured to each anode at suitable places and surrounded by a tubing 8 of insulating material. The en- 2 velope I, after being highly evacuated, may be filled with a fixed gas such as neon or may contain a vapor-producing material such as mercury or sodium. If desired, these gases and materials may be combined. 2

For operating the improved lamp, the two anodes 6 are preferably connected to opposite ends of a secondary transformer winding (not shown) and the cathode 3 connected to the center of this winding through a series currentlimiting resistance. When alternating current is applied to the primary of the transformer, an intermittent discharge is produced between the cathode, which may be heated in any suitable manner, for example, by a transformer, and each of the anodes. The discharge emits light rays, the color of which is determined by the composition of the gas or vapor filling.

After the discharge tube has been in operation for a certain length of time, it has been observed that quantities of dark colored material accumulate in the grooves of the anodes. This material is believed to originate, in part from the active coating on the cathode and in part, from the material vaporized from the anodes themselves. 5 As this vaporized material is deposited in the grooves of the anode surface, instead of on the glass wall, a decrease in the transparency of the glass wall is avoided-with a consequent increase in the light efliciency of the tube.

The anode of the tube is preferably given a dimension such that a minimum satisfactory area is available per unit of current intensity. It is apparent that an anode having an undulated surface, such as described, presents a large area 55 electrode.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An electric discharge device comprising an envelope containing a cathode coated with electronically active material, an anode and an.

ionizable material, said anode being circular and having a corrugated suri'ace, said anode and said cathode being separated an appreciable distance, the length of the corrugations in said anode extending toward said cathode tocollect the material emanating irom said cathode.

2. An electric discharge device comprising an envelope containing a cathode coated with electronically active material, said anode and said cathodebeing separated an appreciable distance, an anode and an ionizable material, said anode being made of corrugated strip having the length of the corrugations extend toward the cathode to collect the material emanating 'i'rom said cathode.

3. An electric discharge device comprising an envelope containing an electrical filamentary cathode coated with electronically active material, a pair oi flat anodes mounted on opposite sides of the cathode and an ionizable material, said anodes being positioned in planes parallel to said cathode and being corrugated, the length the corrugations extending toward the cathode to collect the material emanating from sa cathode.

4. An electric discharge device comprising an envelope containing a thermionic cathode, an anode and a gaseous atmosphere, said anode and said cathode being separated an appreciable distance, said anode being a corrugated strip having the length 01' the corrugations extend toward said cathode to collect the material emanating from said cathode.

5. An electric discharge device comprising an envelope containing a thermionic cathode, an anode and a gaseous atmosphere comprising a metal vapor, said anode and said cathode being separated an appreciable distance, said anode being a corrugated strip having the length of the corrugations extend toward said cathode to collect the material emanating from said cathode.

6. An electric discharge device comprising an envelope containing a thermionic cathode, an anode and a gaseous atmosphere comprising alkali metal vapor, said anode and said cathode being separated an appreciable distance, said anode being a corrugated strip having the length of the corrugations extend toward said cathode to collect the material emanating from said cathode.

7. An electric discharge device comprising an envelope containing a thermionic cathode, an anode and a gaseous atmosphere comprising sodium vapor, said anode and said cathode being separated an appreciable distance, said anode being a corrugated strip having the length of the corrugations extend toward said cathode to collect the material emanating irom said cathode.

WILL-EM UYTERHOE'VEN. 

